How on earth is 1-cos(x) equal to 2sin^2(x/2)?

Limit of (1-cos(x))/x as x approaches 0 | Derivative rules | AP Calculus AB | Khan Academy

Prove that 1+cosx=2cos^2(x/2) and 1-cosx=2sin^2(x/2) trigonometric identites

1-cosx = 2sin^2(x/2) trigonometric identites proof || 1-cos theta

Proof of the Limit (1-cosx)/x as x approaches 0

Integral of 1/(1 + cos x) dx

Limit of (1-cos(x))/x as x approaches 0 | Calculus 1

Prove the Limit as x Approaches 0 of (1-cos(x))/x

integral | indefinite integral | jee Main Jan.9,2020(I)

PreCalculus - Trigonometry: Trig Identities (31 of 57) Proof cos^2(x)=(1+cos2x)/2

Prove (1 - sin x)/cos x = cos x / 1 + sin x

Verify the Trig Identity (1 + cos(x))/sin(x) = csc(x) + cot(x)

Integral 1/(cos(x) - 1)

1+cosx=2cos^2(x/2) trigonometry identites solve || 1+cos(theta)

#Trigonometry all formulas

How To Verify Trigonometric Identities 1/(1+Cosx)+1/(1-Cosx)=2Csc^2x Trigonometry

sin(x) * tan(x/2) = 1 - cos(x)

sin(x) + cos(x) = 1 by Identities (Flawed)

Limit of (1-cos(x))/x^2 as x approaches 0 | Calculus 1 Exercises

Trigonometric Identity sinx/(1 + cos) = (1 - cosx )/sinx